scikits-learn[1] and python2-scikit-learn are duplicate. I notified the author of scikits-learn that is package nameing is incorrect, prior to discovering a package by the correct name already exists, and he seems to be completely unwilling to correct the situation himself.
How to handle this, I don't know (as far as who the maintainer should be), but either scikits-learn should merge into python2-scikit-learn, or scikits-learn should be removed completely. [1] https://aur.archlinux.org/packages/scikits-learn/ [2] https://aur.archlinux.org/packages/python2-scikit-learn/
